1. Field of the Invention
The present invention relates to a highly sensitive color light-sensitive material for use in photography having improved image sharpness.
2. Description of the Prior Art
In color photographic materials, color images which spread or blotted color images must not be formed, distinct images with fine detail, i.e., sharpness, must be obtained and the color particles forming color images must be fine enough that one does not notice that the images are composed of particles.
The sharpness or graininess is determined by the following factors:
(1) THE PARTICLE SIZE DISTRIBUTION OF SILVER HALIDE CRYSTALS AND THE STATE OF THE DISPERSION OF THE SILVER HALIDE CRYSTALS IN AN EMULSION;
(2) OPTICAL PROPERTIES SUCH AS SCATTERING AND REFLECTION OF LIGHT OF VARIOUS WAVELENGTHS UPON EXPOSURE;
(3) CHEMICAL PROPERTIES SUCH AS DEVELOPING SPEED, DEVELOPING EFFECT, ETC.; AND
(4) OTHERS.
Therefore, in order to improve the graininess and/or sharpness, effective countermeasures for at least one of the above-described factors (1) to (4) must be taken and in this respect various suggestions have been made.
Color light-sensitive materials for use in photography comprise at least a yellow-coloring layer, a yellow filter layer, a magenta-coloring layer and a cyan-coloring layer. In order to permit only light which is in a complementary relation with the color image to reach each layer, color light-sensitive materials usually possess a stratum structure in which the cyan-coloring red-sensitive silver halide emulsion layer, the magenta-coloring green-sensitive silver halide emulsion layer, the yellow filter layer and the yellow-coloring blue-sensitive silver halide emulsion layer are arranged in this sequence from the support.
It is empirically known that the visual (or apparent) sharpness of images formed in color light-sensitive materials is most influenced by the sharpness of the magenta image and next most influenced by the sharpness of the cyan image. However, in the conventional stratum structure, the sharpness of the magenta image has been poor since the green-sensitive layer is influenced by light-scattering in the blue-sensitive layer, resulting in the formation of images having apparently poor sharpness. It is true that this problem would be solved by positioning the magenta-coloring layer as the uppermost layer to form a stratum structure in the order of the blue-sensitive layer, the red-sensitive layer, the green-sensitive layer and the yellow filter from the support side, but a serious defect is involved with this layer disposition. That is, since blue light is absorbed by the yellow filter layer, the green-sensitive layer and the red-sensitive layer, the amount of blue light reaching the blue-sensitive layer which possesses a spectral sensitivity for blue light and essentially necessitates blue light is seriously reduced. In other words, the effective sensitivity of the blue-sensitive layer becomes far less (i.e., 1/100-1/1000) than the essential sensitivity of the emulsion. In order to adjust the color balance, the sensitivities of other layers are reduced and, as a result, the sensitivity of the entire light-sensitive material becomes extremely low. Further, when tungsten light is used as a light source, the sensitivities of the red-sensitive layer and the green-sensitive layer must be reduced to lower than that of the blue-sensitive layer in order to adjust the color balance, since the light source itself contains less blue light component and more red light component. Therefore, it has actually been impossible to form a stratum structure of a highly sensitive color light-sensitive material for photography using the above-described latter sequence. In order to remove this defect, U.S. Pat. No. 3,658,536 discloses a stratum structural configuration in which only part of the blue-sensitive layer is provided under the green-sensitive or red-sensitive layer and the rest is allowed to remain at the uppermost side, thus obtaining the effective sensitivity of the blue-sensitive layer and reducing the influence of light scattering on the green-sensitive layer to improve the sharpness with a high sensitivity being maintained.